This invention relates to apparatus and a method of augmenting the maxilla of a candidate for a dental implant by filling part of the patient's maxillary sinus cavity with bone and, more particularly, to a device that closes the sinus cavity when the Schneiderian membrane is torn during surgery intended to lift the membrane from the floor of the sinus cavity and add bone under the membrane. The maxillary sinuses of a person are located on each side of the maxilla between the canine eminence and the tuberosity. The lowest point of the sinus floor usually lies superior to the first molar and the second premolar. However, maxillary sinus shapes vary greatly from one side of a person's face to the other, and from individual to individual.
As a person ages, the maxillary sinuses grow at the expense of the bone. Also, disease may cause resorption of the bone surrounding the sinus. When bone loss occurs between the sinus floor and the dental arch, the feasibility of using maxillary dental implants is decreased.
Dental or oral implants are blades or screws with attached posts. These implants are surgically implanted in a patient's mandible or maxilla along the occlusal plane. The implantation is achieved by exposing the bone with an incision through the gum tissue and creating a groove or bore in the bone with a burr or drill. The implant blade is then wedged into the groove or bore so that the post protrudes. Then the tissue is sutured about the bone and the base of the post. Finally, the post is used to mount an artificial dental appliance, such as a bridge. This procedure can be carried out in stages over several months.
A patient with an enlarged maxillary sinus has little bone in the maxillary dental arch for accommodating the insertion of an implant. Consequently, the implantation procedure may result in the penetration of the Schneiderian membrane on the sinus floor and the sinus itself. This may promote sinus infection and may result in the implant being only loosely held in the remaining bone, so that it fails to function effectively as a support for artificial teeth.
In U.S. Pat. No. 4,521,192 of the present inventor, there is suggested a technique for lifting the Schneiderian membrane and locating bone fragments beneath it in order to thicken the bone at the sinus floor by regrowth of new bone around the inserted the bone fragments. According to this suggestion, an implant is used which has a basket or cradle built into the blade portion. This basket is open toward the groove in the patient's bone and is filled with bone chips or fragments. Consequently, when the blade is wedged in the groove, the basket is moved to the base of the groove which, if the Schneiderian membrane is exposed, pushes the membrane upward into the maxillary sinus cavity.
The depth at which the blade of an implant is located in the patient's bone cannot be varied to any great extent with this prior apparatus. Thus, with this prior device, in which the basket is fixed to the blade portion of the implant, there is little control over the degree to which the Schneiderian membrane is lifted. This limits the oral surgeon's ability to increase the thickness of bone at the floor of the sinus cavity and to make it suitable for the retention of the implant.
Another technique for augmenting the mandible of a patient with additional bone in order to support a dental implant is disclosed in U.S. Pat. No. 4,682,951 of the present inventor. According to the disclosure in that patent a bone chip container which is adjustably secured to the implant is used for installing the implant in the maxilla of a patient in which the bone of the dental arch in an edentulous span is thin because of a descending maxillary sinus. In using the device, an edentulous area of the dental arch of the maxilla is exposed. A groove is made in the bone mesial and distal to the floor of the sinus, and up to the Schneiderian membrane, which membrane lies on the floor of the maxillary sinus. In addition a larger opening is made through the bone toward the center of the groove. Then an especially designed sinus lift implant is installed in the groove.
The sinus lift implant has a container which is open at one side such that it is in the form of a cradle or basket. The basket has a size such that it can pass through the opening at the center of the groove made in the bone. Threaded apertures are located in the bottom of the basket of the blade and threaded shafts engage these apertures. The blade or base portion of the implant is narrow, at least at its ends, so that it can be wedged tightly in a portion of the groove in the bone at such a depth such that the base does not extend downwardly from the maxilla beyond the existing bone of the dental arch. One or more posts project downwardly from the base and can be used to mount an artificial tooth structure from the maxilla.
During installation, the open basket is filled with bone chips, either natural or artificial. Then the basket is passed up into the large opening in the maxilla below the Schneiderian membrane. The blade portions (mesial and distal) to the basket are then tapped into place so that the implant is wedged in the groove and the basket is at least flush with the alveolar crest. Access to the ends of the threaded shafts are provided through the bottom of the apertures in the base so that the shafts can be rotated. Rotation of these shafts raises, lowers or tilts the basket to redefine the shape and thickness of the sinus floor. The basket is then moved high into the maxillary sinus, although still below the Schneiderian membrane. Its base is now well above the alveolar crest so that it is easy to suture close the tissues beneath it.
Once in position, the gum tissue is sutured closed over the base portion. During a period of several weeks or months, new bone will grow and fuse with the surrounding bone and chips. This results in a thicker bone area enclosing the implant and a reduction in the size of the sinus. After the formation of the new bone, the artificial tooth structure is mounted on the post of the implant, which post protrudes beyond the gum tissue.
The posts themselves can be made independently from the implant itself, thus allowing the implant to be completely submerged during the healing process.